Variable-size mixer for high gain range transmitter

ABSTRACT

Implementations of a high gain range transmitter with variable-size mixers are described.

BACKGROUND

Typical communication systems, employing communication standards such asGSM (Global System for Mobile Communication), GPRS (General Packet RadioService), EDGE (Enhanced Data Rates for GSM Evolution), UMTS (UniversalMobile Telecommunication Systems), and combinations (multi-modesystems), may use transceivers for transmitting and receiving signals. Atransceiver can include a high gain range transmitter to transmitsignals to communication devices when using any of such communicationstandards.

In a non-constant envelope phase modulation scheme, a baseband signalcontaining a baseband phase signal and a baseband amplitude signal ismodulated into a high frequency carrier signal, such as a radiofrequency (RF) frequency signal or RF signal, for transmission. Thebaseband phase signal may phase modulate the RF frequency carrier signalproducing a phase modulated RF signal. The phase modulated RF signal mayfurther be amplitude modulated by the baseband amplitude signal in amixer component to produce the non-constant envelope phase modulated RFsignal. The amplitude modulation may be sourced from a Digital to AnalogConverter (DAC) which transforms the baseband amplitude signal into ananalog baseband amplitude signal. The amplitude modulation may be usedfor exact trajectory of the phase modulated RF signal and may require ahigh gain range for efficient transmission in a transmitter.

Normally, a transmitter employed in a polar modulation may require ahigh gain range for transmitting the non-constant envelope phasemodulated RF signal. However, present-day mixers are generally notcapable of handling high gain ranges. To handle high gains, the mixermay require a larger size which may lead to a distortion problem duringa low gain transmission of the modulated RF signal. Furthermore, thelarger mixer size produces a relatively high local oscillator (LO)leakage which includes a non-zero RF signal when the baseband amplitudesignal is zero. Therefore, a conventional topology of the transmitter ina typical communication device may not meet low distortion and low LOleakage requirements.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Thesame numbers are used throughout the drawings to reference like featuresand components.

FIG. 1 is a block diagram illustrating a transmitter component.

FIG. 2 is a block diagram illustrating a process of phase modulationwith amplitude modulation.

FIG. 3 is a block diagram illustrating an exemplary transmission sectionof a modulator implemented with variable-size mixers.

FIG. 4 is a block diagram illustrating an exemplary implementation of aRF Digital-to-Analog Converter (DAC) used in a transmitter.

FIG. 5 is a block diagram illustrating an exemplary mixer implemented ina transmitter.

FIG. 6 is a flowchart illustrating an exemplary method for implementinga transmitter with variable-size mixers in a communication device.

DETAILED DESCRIPTION

This disclosure is directed towards techniques and methods forimplementing a high gain range transmitter with a variable-size mixer ina communication device. The high gain range transmitter with thevariable-size mixer can be included in a radio frequency (RF) componentof a transmitter. The high gain range transmitter modulates a basebandsignal into an RF frequency carrier and produces a modulated RF signal.The modulated RF signal may include a non-constant envelope phasemodulated RF signal produced through a mixer component. The mixercomponent may be susceptible to distortion and local oscillator (LO)leakage in the transmitter output. To achieve low distortion and LOleakage over a high gain range, the mixer component used in aconventional topology is subdivided into smaller sub-mixer components.

FIG. 1 illustrates a transmitter 100 that includes a baseband component102 and an RF component 104, providing transmission and reception ofdata. The baseband component 102 may produce a baseband signal used tomodulate an RF frequency carrier of the RF component 104. The RFcomponent 104 may provide the RF frequency carrier, which is phasemodulated and amplitude modulated to produce a non-constant envelopephase modulated RF signal. In an implementation, the RF component 104includes a set of subdivided mixer (sub-mixer) components to produce thenon-constant envelope phase modulated RF signal. The set of sub-mixercomponents may include a single output to produce an output equivalenceof the larger mixer used in the conventional topology. A phase modulatedRF signal (also referred to as a local oscillator signal) may bereceived by the set of sub-mixer components, and amplitude modulated toproduce the non-constant envelope phase modulated RF signal.

A signal from peripherals, camera, display etc. 106 may be received byInput/Output component (I/O) 108 for initial processing. The I/Ocomponent 108 may convert analog data signals into digital data signals,while the digital data signals may be maintained in the same state(i.e., remain digital). The I/O component 108 may process the datasignals to produce an In-phase signal (I) and a Quadrature phase signal(Q).

The data signals output of I/O component 108 goes through path 110, andare received by a digital signal processor (DSP) 112. The DSP 112 mayuse a filter to limit the bandwidth, forming a spectrum of the basebandsignal. The DSP 112 may include a Coordinate Rotation DIgital Computer(CORDIC) component to transform the I and Q signals of the basebandsignal into equivalent polar representations. The polar equivalence maycontain the baseband phase signal and the baseband amplitude signal.

A digital interface 114 may connect the path for DSP 112 output which isreceived by a Phase Locked Loop/Modulator 116 component. The digitalinterface 114 may provide a bi-directional communications between thebaseband component 102 and the RF component 104. The Phase LockedLoop/Modulator 116 component may perform phase modulation and amplitudemodulation of the RF frequency carrier. In an implementation, the PhaseLocked Loop/Modulator 116 component may include the phase locked loop(PLL) component for phase modulation of the RF frequency carrier, a setof subdivided DAC (sub-DAC) components to transform the digital basebandamplitude signal into analog baseband signals, and the set of sub-mixercomponents for amplitude modulation of the phase modulated RF signal.

The non-constant envelope phase modulated RF signal from the output ofPhase Locked Loop/Modulator component 116 may pass through path 118, andreceived by an amplifier 120. The amplifier 120 may amplify thenon-constant envelope phase modulated RF signal before transmissionthrough an antenna 122.

FIG. 2 illustrates a block diagram 200 that provides a transformation ofthe data signals by DSP 112 into a polar equivalent baseband signal, andphase/amplitude modulation by the Phase Locked Loop/Modulator component116 to produce the non-constant envelope phase modulated RF signal. Adigital baseband signal processing component 202 may filter the I and Qsignals in order to produce the baseband signal. The baseband signal atthe output of digital baseband signal processing component 202 includesthe I signal passing through path 204 and the Q signal passing throughpath 206.

The I and Q signals on path 204 and path 206 respectively, are receivedby the CORDIC 208. The CORDIC 208 transforms I signal and Q signal intotheir polar equivalence, which includes the baseband phase signal outputon path 210 and the baseband amplitude signal output on path 212. Thebaseband phase signal output on path 210 is received by a phasedifferentiator 214 component which transforms the baseband phase signalinto a baseband modulating frequency signal. The baseband amplitudesignal output on path 212 is received by a digital multiplier 216 whichmay include multiplication of the baseband amplitude signal on path 212by a programmable value in order to implement gain control (i.e.,transmitted power level is regulated). The digital multiplier 216 mayturn ON a portion or entire set of sub-mixer components, based upon thetransmitted power level that is regulated in the digital processing ofthe baseband amplitude signal on path 212. A path 218 may include adigitally processed baseband amplitude signal output of the digitalmultiplier 216 and received by a RF DAC component 220. The RF DACcomponent 220 may convert the digitally processed baseband amplitudesignal into the analog baseband signals. As discussed below, the RF DACcomponent 220 includes the set of sub-DAC components i.e., sub-DACcomponents 220-1, 220-2, . . . 220-N, where “N” is an integer.

The baseband modulating frequency signal may pass through path 222 andreceived by a PLL 224. The PLL 224 may be used to modulate the RFfrequency carrier, with the baseband modulating frequency signal frompath 222, to produce the phase modulated RF signal on path 226. Thephase modulated RF signal on path 226 may contain a differential signalwhich is received by a mixer component 228. The mixer component 228, asdiscussed below, includes the set of sub-mixer components 228-1, 228-2,. . . 228-N which are connected in parallel. An individual sub-mixercomponent (e.g., sub-mixer component 228-1) processes a fraction of theanalog baseband signals, and is proportional in size to a maximum levelof the fraction of the analog baseband signals received (i.e., by theindividual sub-mixer component). The sum of the fractions is equal tothe whole baseband signal. As discussed below, the processing of smallersignals reduces the local oscillator leakage and distortions. Thedifferential signal received by the mixer component 228 may include apositive signal (i.e., LO signal) and a negative signal (i.e., LOXsignal) of the phase modulated RF signal on path 226. The differentialsignal received by the mixer component 228 may undergo amplitudemodulation from a signal on path 230. The signal on path 230 includesthe output of the RF DAC component 220 which contains the analogbaseband signals. The output of the RF DAC component 220 includes afirst analog baseband signal, a second analog baseband signal and so on.As shown below, the first analog baseband signal may include an outputof the first sub-DAC component 220-1, the second analog baseband signalmay include an output of the second sub-DAC component 220-2, and so on.

FIG. 3 illustrates a block diagram 300 illustrating an exemplaryimplementation of a modulator component which includes the sub-DACcomponents 220 and the sub-mixer components 228. The sub-mixercomponents 228 include an adder component 314. The exemplaryimplementation of the modulator component decreases the distortion andthe LO leakage in an output frequency signal. The order in which theblocks of the system are described is not intended to be construed as alimitation, and any number of the described system blocks can becombined in any order to implement the system, or an alternate system.Additionally, individual blocks may be deleted from the system withoutdeparting from the spirit and scope of the subject matter describedherein. Furthermore, the system can be implemented in any suitablehardware, software, firmware, or a combination thereof, withoutdeparting from the scope of the invention

The digitally processed baseband amplitude signal from path 218 isreceived by the RF DAC component 220 which is subdivided into “N”sub-DAC components i.e., sub-DAC components 220-1, 220-2, . . . 220-N,collectively referred to as the set of sub-DAC components 220. The setof sub-DAC components 220 may transform the digital baseband signal frompath 218 into N analog baseband signals i.e., analog baseband signals230-1, 230-2, . . . 230-N. As there are N outputs, there can be Ncorresponding set of sub-mixer components in the mixer component 228(i.e., sub-mixer components 228-1, 228-2, . . . 228-N), hereinafterreferred to as the set of sub-mixer components 228. The set of sub-mixercomponents 228 receives the N analog baseband signals (i.e., analogbaseband signals 230-1, 230-2, . . . 230-N), from the set of sub-DACcomponents 220. The set of sub-mixer components 228 includes individualsizes that are proportional to a maximum output current (i.e., maximumlevel) produced by the corresponding set of sub-DAC components 220(i.e., analog baseband signals 230-1, 230-2, . . . 230-N). The set ofsub-mixer components 228 may be independently switched ON and OFF. Theswitching ON and OFF is determined by the transmitted power level thatis regulated in the digital processing of the baseband amplitude signal.The switching ON and OFF of the set of sub-mixer components 228 isfurther determined by the amplitude modulation as further discussedbelow.

In an implementation, if some of the set of sub-mixer components 228 donot receive the analog baseband signals during a transmission burst(e.g., there is a decrease in transmission gain as implemented by thedigital multiplier component 216), then the part of the set of sub-mixercomponents 228 can be switched OFF during the entire transmission burst.The switched OFF part of the set of sub-mixer components 228, during theentire transmission burst, is hereinafter referred to as a first subsetof the set of sub-mixer components 228. The first subset may include oneor more sub-mixer components from the set of sub-mixer components 228that do not receive the analog baseband signals due to the gain controlregulation (e.g., based on a desired signal level of the outputfrequency signal). The other one or more sub-mixer components that mayreceive the analog baseband signals (i.e., turned ON) are included in asecond subset of the set of sub-mixer components 228. The switching OFFof the first subset during the entire transmission burst may allow adecrease in the LO leakage.

In another implementation, if the second subset of the set of sub-mixercomponents 228 does not process the analog baseband signals during apart of the transmission burst (e.g., due to amplitude modulation), thenthe second subset may be dynamically turned ON and OFF to furtherdecrease the LO leakage. The dynamic switching of the second subset maycontinue if the digital multiplier component 216 does not introduce anew adjustment in the gain control regulation. The second subset (i.e.,number of sub-mixer components) may further be based upon the desiredsignal level of the output frequency signal in the modulator. As such,the number of sub-mixer components to be used may be determined basedupon the gain regulation and the amplitude modulation to be implementedin the output frequency signal.

A path 302 may supply the positive side (i.e., LO signal) of thedifferential signal in the phase modulated RF signal on path 226. Inconjunction with the positive side, a path 304 also supplies thenegative side (i.e., LOX signal) of the differential signal in the phasemodulated RF signal on path 226. The LO and LOX signals may be receivedby buffer components 306-1, 306-2, . . . and 306-N, collectivelyreferred to as the buffer component 306. The buffer components 306-1,306-2, . . . and 306-N are respectively connected to the set ofsub-mixer components 228. The buffer component 306 regenerates the localoscillator signal, allowing optimum driving conditions to the sub-mixercomponents 228. The buffer component 306 may be enabled by enable switchcomponents 308-1, 308-2, . . . 308-N, collectively referred to as enableswitch components 308. The enable switch components 308 are respectivelyconnected to the buffer component 306. The enable switch components 308may be used to turn OFF and ON the subset of the set of sub-mixercomponents 228. The buffer component 306 may include N output signalsthat passes through paths 310-1, 310-2, . . . , and 310-N. The N outputsignals on paths 310-1, 310-2, . . . and 310-N are respectively receivedby the set of sub-mixer components 228. The set of sub-mixer components228 mixes the N analog baseband signals to the corresponding N outputsignals on paths 310-1, 310-2, . . . and 310-N. To this end, thesub-mixer component 228-1 may provide a first modulated signal output,the sub-mixer component 228-2 may provide a second modulated signaloutput, and so on.

The first modulated signal output, the second modulated signal output,and so on, may pass through a path 312 and received by an addercomponent 314. The adder component 314 combines the first modulatedsignal output, the second modulated signal output, and so on, from path312. To this end, the adder component 314 produces an output frequencysignal which includes the non-constant envelope phase modulated RFsignal in the given implementation.

In an implementation, the enable switch component 308-1 may turn ON thebuffer component 306-1 to supply differential signals LO and LOX, frompaths 302 and 304 respectively, to the sub-mixer component 228-1. Thesub-mixer component 228-1 mixes the differential signals LO and LOX,with the analog baseband signal from path 230-1. An output of thesub-mixer component 228-1 may include the first modulated signal outputthat will be added to the output of the rest of the set of sub-mixercomponents 228 (i.e. sub-mixer component 228-2, 228-3, . . . 228-N). Thesum of the output (i.e., using the adder component 314) of the set ofsub-mixer components 228 may include the non-constant envelope phasemodulated RF signal on path 118. The sub-mixer component 228-1 may bedisabled dynamically, for part of the transmission burst, if thesub-mixer component 228-1 is not receiving any analog baseband signalsdue to amplitude modulation. In other words, the dynamic switching ofthe sub-mixer component 228-1 may be determined by an instantaneousvalue of the varying baseband signals based on the amplitude modulation.

FIG. 4 illustrates an exemplary implementation of a multi-bit set ofsub-DAC components 220 (e.g., 10-bit thermometer-coded DAC) to achievelinear output with minimum distortion and LO leakage in the set ofsub-mixer components 228 as previously described.

The digitally processed baseband amplitude signal on path 218 may bereceived and converted by the multi-bit set of sub-DAC components 220into analog baseband signals. In an implementation, the multi-bit set ofsub-DAC components 220 may include 2¹⁰-1 switchable current source cellsthat can be turned ON corresponding to a 10 bit digital inputrepresenting the digitally processed baseband amplitude signal from path218. Each DAC cell in the multi-bit set of sub-DAC components 220 mayinclude an active current source which is grounded when not activated,or switched to the corresponding path 230 (e.g., path 230-1, 230-2, . .. 230-32) if activated.

In the present example, the multi-bit set of sub-DAC components 220includes 2¹⁰-1 or 1023 DAC cells that are subdivided and arranged in2^(10/2) rows and columns, i.e. 32 rows by 32 columns. The arrangementof 32 rows and 32 columns is shown in FIG. 4. The 32 columns arereferred to as path 400-1 for Column 1, path 400-2 for Column 2, . . . ,path 400-32 for Column 32; and similarly, the 32 rows are referred to aspath 402-1 for Row 1, 402-2 for Row 2, . . . , path 402-32 for Row 32.Each column shows 32 DAC cells; however, the first column (Column 1)shows 31 DAC cells. In this example, the 32^(nd) or last DAC cell in theColumn 1 is empty or “null” and is represented as 404.

The DAC cells in each column are grouped together, where each group canbe designated as a sub-DAC component. Since there are 32 columns, therecan be 32 groups resulting in 32 sub-DAC components. The 32 sub-DACcomponents include sub-DAC 220-1, sub-DAC 220-2, up to sub-DAC 220-32.The DAC cells in each column (e.g., columns 1, 2, 3, . . . 32) areconnected together to form a single output sub-DAC component asmentioned (e.g., sub-DAC 220-1, 220-2, . . . 220-32). The single outputsub-DAC component may include the maximum output current that isproportional to the size of the variable-size mixer used in the highgain range transmitter. The multi-bit set of sub-DAC components 220processes a decimal coded value of the digital baseband amplitude signalon path 218 that is between 0 and 1023 by turning ON the correspondingnumber of DAC cells between 0 and 1023. For example, a decimal code 100may be received by a 10-bit thermometer coded set of sub-DAC components220 and converted into the analog baseband signals on path 230. Thedecimal code 100 may correspond to each and every DAC cell of the first3 columns (i.e., 400-1, 400-2, and 400-3) and also the first 5 DAC cellsof the 4^(th) column (i.e., 400-4) of the multi-bit set of sub-DACcomponents 220. The corresponding DAC cells are activated to ON state,thereby producing the analog baseband signals on path 230-1, path 230-2,path 230-3, and path 230-4 from the 4 sub-DAC components (e.g., sub-DAC220-1, 220-2, 220-3 and 220-4). The 4 sub-DAC components (e.g., sub-DAC220-1, 220-2, 220-3 and 220-4) output may be received by thecorresponding sub-mixer components (e.g., sub-mixer 228-1, 228-2, 228-3and 228-4) as shown in FIG. 4, to produce the non-constant envelopephase modulated RF signal.

In the example just described (i.e., decimal code 100 received by themulti-bit set of sub-DAC components 220), if the gain control regulationrequires the first subset to include sub-mixers 228-5, 228-6, . . .228-N, then the dynamic switching due to the amplitude modulation may beimplemented only on the sub-mixers 228-1, 228-2, 228-3, and 228-4. Thesub-mixers 228-1, 228-2, 228-3, and 228-4 are included in the secondsubset of the set of sub-mixer components 228. As discussed above, thesecond subset of the set of sub-mixer components 228 continues to beswitched dynamically, if no new adjustment is introduced by the gaincontrol regulation.

FIG. 5 illustrates an exemplary schematic diagram of the sub-mixer 228-1implemented for modulation in a transmitter. The schematic diagram hasbeen described with respect to one of the mixer component 228, and mayinclude electronic components such as transistors, current sources, avoltage supply, and so on. The schematic diagram intends to provide abasic conceptual description of the sub-mixer 228-1 and does not limitthe number of components present in the mixer component 228. In thefollowing description, the components common to FIGS. 1-4 have beenreferred to by the same names and reference numbers.

In an implementation, the circuit of the sub-mixer 228-1 can beimplemented via a differential NMOS circuit. The differential NMOScircuit can be realized with the use of n-channel MOSFETs 500-1, 500-2,. . . , 500-6 referred to respectively as NMOS 500-1, NMOS 500-2, . . ., NMOS 500-6, hereinafter. A common-source terminal of the NMOS 500-1and the NMOS 500-2 may receive the analog baseband signal from path230-1 and implement mixing of the analog baseband signal 230-1 with thedifferential signals LO and LOX received on paths 302 and 304respectively. In certain embodiments, the differential input to the NMOS500-1 and the NMOS 500-2 (i.e., LO and LOX signals) may use a buffercomponent where the enable signal 308-1 may be connected to turn ON orOFF the sub-mixer 228-1.

The NMOS 500-3 and the NMOS 500-4 may be implemented as cross-coupledtransistors to cancel a charge-injection through gate-to-draincapacitances of NMOS 500-1 and NMOS 500-2, respectively. Furthermore,the NMOS 500-5 and the NMOS 500-6 may be cascode transistors to bufferthe modulated RF signal output. The source terminals of the NMOS 500-5and the NMOS 500-6 may receive current signals from a current source502-1 and a current source 502-2 to keep the NMOS 500-5 and NMOS 500-6biased at all gains. The gate terminals of the NMOS 500-5 and the NMOS500-6 are driven by a voltage VCASC 504 for optimal operation. Thedifferential output path 506-1 and path 506-2 are connected with thedifferential output of the rest of the set of sub-mixer components(e.g., sub-mixer 228-2, 228-3, . . . 228-N), to produce an outputequivalence of the larger mixer component used in conventional topologyless the distortions and LO leakages.

FIG. 6 illustrates an exemplary method 600 for reducing distortion andlocal oscillator (LO) leakage. The exemplary method 600 is describedwith reference to FIGS. 1-5. The order in which the method is describedis not intended to be construed as a limitation, and any number of thedescribed method blocks can be combined in any order to implement themethod, or alternate method. Additionally, individual blocks may bedeleted from the method without departing from the spirit and scope ofthe subject matter described herein. Furthermore, the method can beimplemented in any suitable hardware, software, firmware, or acombination thereof, without departing from the scope of the invention.

At block 602, determining a number of sub-mixer components is performed.For example, the number of sub-mixer components (e.g., sub-mixercomponents 228) to be used is determined based on a signal level of anoutput frequency signal.

At block 604, switching ON the number of sub-mixer components isperformed. In an implementation, the number of sub-mixer components(e.g., second subset of the set of sub-mixer components) is turned ON toproduce the output frequency signal.

At block 606, switching OFF the rest of the sub-mixer components isperformed. For example, the rest of the sub-mixer components (e.g.,first subset of the set of sub-mixer components) that were not turned ONin block 604, are turned OFF.

Conclusion

Although the subject matter has been described in language specific tostructural features and/or methodological acts, it is to be understoodthat the subject matter defined in the appended claims is notnecessarily limited to the specific features or acts described. Rather,the specific features and acts are disclosed as exemplary forms ofimplementing the claims. For example, the systems described could beconfigured as wireless communication devices, computing devices, andother electronic devices.

What is claimed is:
 1. A modulator component that generates an outputfrequency signal comprising: a radio frequency (RF) digital to analogconverter (DAC) component that receives and converts a digitallyprocessed baseband signal, and outputs a first analog baseband signaland a second analog baseband signal; a first sub-mixer component thatmodulates the first analog baseband signal and a frequency signal togenerate a first modulated signal; a second sub-mixer component thatmodulates the second analog baseband signal and the frequency signal togenerate a second modulated signal; an adder component that receives thefirst modulated signal and the second modulated signal and provides theoutput frequency signal; wherein the first sub-mixer component and thesecond sub-mixer component are independently switched ON and OFF.
 2. Themodulator component of claim 1, wherein the RF DAC component includesmultiple DAC cells.
 3. The modulator component of claim 2, wherein theRF DAC component includes the multiple DAC cells that are subdivided toform N sub-DAC components connected to N sub-mixer components.
 4. Themodulator component of claim 1, wherein the RF DAC component receivesand converts the digitally processed baseband signal for amplitudemodulation.
 5. The modulator component of claim 1, wherein the firstsub-mixer component is proportional in size to a maximum level of thefirst analog baseband signal.
 6. The modulator component of claim 1,wherein switching ON and OFF is determined by on of the following: bytransmitted power lever based on the digitally processed basebandsignal, or by an instantaneous value of the first analog baseband signaland the second analog baseband signal, wherein the analog basebandsignals vary due to amplitude modulation.
 7. The modulator component ofclaim 1, wherein the first sub-mixer component and the second sub-mixercomponent are connected in parallel.
 8. The modulator component of claim1, further comprising buffer components to supply a local oscillator(LO) signal to the sub-mixer components.
 9. The modulation component ofclaim 1, wherein at least one of the first and second sub-mixercomponents is OFF/ON switchable.
 10. An apparatus, comprising: DAC cellswhich include active current sources; a subdivided DAC (sub-DAC)component which includes one or more of the active current sources andprovides analog baseband signals, wherein the RF DAC component outputs amodulating signal which includes the analog baseband signals; and asub-mixer component coupled to the sub-DAC component, the sub-mixer tobe dynamically turned On and OFF based on at least amplitude modulationassociated with an out put frequency signal of the apparatus.
 11. Theapparatus of claim 10, wherein the DAC cells receive and convertdigitally processed baseband signals into the analog baseband signals.12. The apparatus claim 11, wherein the DAC cells receive the digitallyprocessed baseband signals for amplitude modulation.
 13. The apparatusof claim 10, wherein the DAC cells are subdivided to form N sub-DACcomponents.
 14. The apparatus claim 13, wherein the DAC cells includethe N sub-DAC components that provide the analog baseband signals to theN sub-mixer components.
 15. The apparatus of claim 10, wherein the DACcells are grounded when not activated.
 16. The apparatus of claim 10,wherein the sub-mixer is further to be dynamically turned ON or OFFbased a gain control regulation of output frequency signal.
 17. Theapparatus of claim 10, wherein the sub-mixer is further to bedynamically turned ON or OFF to mitigate local oscillator leakage.
 18. Amethod of reducing local oscillator (LO) leakage in a modulator thatgenerates an output frequency signal and having a set of sub-mixercomponents comprising: determining a number of sub-mixer components tobe used based on a signal level of the output frequency signal generatedby the modulator; switching ON the number of sub-mixer components to beused; switching OFF the remaining sub-mixer components in the set ofsub-mixer components and dynamically switching an operational state ofthe number of sub-mixer components to be used based on a condition ofthe output frequency signal.
 19. The method of claim 18, wherein thenumber of sub-mixer components is determined based on gain regulation ofthe output frequency signal.
 20. The method of claim 18, wherein thenumber of sub-mixer components is determined based on amplitudemodulation of the output frequency signal.
 21. The method of claim 18,wherein individual sub-mixer components in the set of sub-mixercomponents are proportional in size to a maximum level of the analogbaseband signals received by the individual sub-mixer components. 22.The method of claim 18 further comprising a buffering componentsupplying LO signals to the set of sub-mixer components.
 23. The methodof claim 18, wherein the output frequency signal is a transmission burstand the condition is amplitude mosulatioin.